也门1区块恶性漏失地层气体钻井实践

Practice of Gas Drilling in Severe Loss Formation of Yemen Block 1

摘要:

也门1区块地表覆盖着约300 m厚坚硬灰岩，区块内断层多，广泛存在着漏失层，采用常规钻井技术，机械钻速慢，井漏频繁，钻井难度很大。从地质条件、循环介质以及经济性等方面评价了气体钻井在1区块的适应性。现场应用初期，砂岩地层井漏、下套管遇阻问题非常突出，气体钻井发挥的作用有限。针对这些问题，通过优化井身结构和注气注液参数，优选泡沫、充气钻井基液配方、首选充气盲钻作为快速钻穿恶性漏失层的主要技术等，并制订完善的技术措施。现场3口井的应用表明，1区块地层复杂，单一的空气、泡沫或气体钻井技术只能解决部分钻井问题，综合运用气体钻井技术，才能满足提高钻速、稳定井壁和预防井漏等多方面的要求，从整体上提高钻井时效。

Abstract:

This paper focuses on field experience in block 1 of Yemen Republic. The wells have to be drilled through hard limestone and severe fractured thief zone. Low rate of penetration (ROP) and total mud loss were encountered during drilling operations. On the basis of geological characteristics, drilling fluids and economy, the adaptability of gasified fluids drilling in block 1 was evaluated. At the beginning of field application, gasified fluids drilling was only used in the surface interval because some downhole problems, such as lost circulation in sand formation with aerated fluids and the casing stuck. According to these problems, the well structure, air and fluids injection parameters, formulas of foam and aerated base fluids were optimized, and aerated blind drilling was chosen as the principal means to penetrate the severe lost circulation formation, the perfect technical measures were also formulated. The experience of 3 field wells showed that with only air, only foam or only aerated fluid could deal with a part of drilling problems; the integrated application of gas drilling could satisfy the requirements of ROP improvement, borehole wall stability and leakage prevention.